The edge-lit panels with emergency light signs such as a lighted exit sign are well known in the art. Exit signage using photo-luminescent (PL) materials are becoming more and more popular in the industry. The majority of these products are not internally powered and the PL coating of the legend in the panel is charged in the ambient light. During a power failure the EXIT legend provides passive illumination (glow) for several hours. The main disadvantage of this method is that the performance of the exit sign depends on the ambient light level. Furthermore, the equipment must be installed at a specified distance from a permanent light source, which has to deliver a specified minimum luminance level.
Other solutions such as in U.S. Pat. No. 6,364,498 use EXIT signs with translucent legends where the PL coating is energized by the equipment's own light source, and is positioned behind the legend i.e., back-lit. This solution does not need ambient lighting for functioning. It uses a dual mode illumination, the active lighting with its own light source installed behind the display and passive lighting with photo-luminescent pigment coated on the display panel.
Alternative solutions of EXIT signage for emergency lighting use display panels with the active light source positioned on the edge of the display i.e. edge-lit, instead of back-lit. One such solution is shown and described in a co-pending commonly assigned U.S. patent application Ser. No. 10/898,649, filed Jul. 23, 2004 entitled, “Cold-Cathode Fluorescent Lamp Assembly for Lighting Applications”. This application is incorporated by reference herein for all purposes. FIGS. 1 and 2 show typical methods of manufacturing edge-lit panels 10 for EXIT signs with a legend 11 and a contour 12. The light source 13 is applied on the panel edge, perpendicular to the display surface. The display i.e. legend 12 is illuminated as an effect of the multiple reflections 14 and refractions 15 of the light beams on the panel front 10a and back surfaces 10b. The legend coating 12 is applied either on the back 10b of the panel 10 as shown in FIG. 1 or on the panel front face 10a as shown in FIG. 2, with this second option allowing for a better background illumination.
It is thus desirable to provide an improved edge lit panel having improved and extended visibility.